Echinopsis subdenudata &nbsp &nbsp 5/9/19 I can never cease marveling over how little actual soil will make a cactus happy (?). This little plant is several years old. It's never had more than the roughly 3 cubic centimeters of soil you see in my fingers. The soil, by the way, is standard Cornell mix, modified for cactus. (one gallon peat (MUST BE CANADIAN SPHAGNUM PEAT; NEVER USE ANY OTHER KIND), one gallon vermiculite, and the modification - one gallon of perlite or pumice. One cup composted cow manure for trace elements and two level tablespoons of fine granular limestone (I prefer the dolomite flavor) to run the pH up to where most plants need it. If you are growing epiphytes (xmas cacti, orchids, etc.) don't add the limestone. You should water always with a dilute fertilizer solution. I use 1/8 teaspoon of Peters 20-20-20 per gallon of water. Be sure to get the stuff with trace elements added. There is never a reason to re-pot any plant using this mix, unless you want the plant to get bigger. The CSSNM website has an article I wrote on this synthetic soil (see Information about Plants). (01/88)